The present invention relates to an apparatus for measuring the temperature of a substance to be heated in a high electric field of microwaves.
When it is desired to know the temperature of a substance heated in a microwave heater, a probe such as a thermocouple may be inserted into an electronic range without any impediment if the electronic range is a household one having an electric field strength of an oscillation output of about 600 W to 1 KW. However, in the case of an industrial microwave heater having a high electric field strength of an oscillation output above 1 KW, employment of the probe brings about such disadvantages that abnormal heating occurs in the probe and that disconnection or the like is caused by a discharge of a probe cable element or others, and thus satisfactory measurement can not be carried out.
Even when a non-contact type thermometer such as an infrared radiation thermometer is employed to measure a temperature from outside of the heater so as to avoid the effect of the high electric field of the microwaves, accurate measurement of the temperature can not be performed as the inside of the heater is filled with water vapor, a decomposition gas, etc. generated from the substance to be heated.
To cope with these disadvantages, measurement has been conducted heretofore by inserting a thermocouple into the heater after microwave heating has been stopped.
Much inconvenience and many problems are caused by the above-described conventional temperature measurement wherein the microwave heating is stopped for each temperature measurement in an environment of high temperature or high radiation.